Communication cables, such as electrical and fiber optic cables, are often spliced or stored in duct work or an enclosure for later expansion of a network. The cables are normally jacketed in a sealed enclosure that has to be invaded in order to make the desired splice connection. Problems sometimes exist due to a poorly sealed cable assembly. Various designs have been employed to minimize adverse cable splice exposure.
One problem that sometimes occurs is that due to deterioration of various materials, or for expansion of a cable assembly after a period of time, a seal assembly may have to be repaired, or re-penetrated in the field. Unfortunately, various terminals, enclosures, and seal assemblies presently available are not particularly installer friendly. In some instances, an undesired manual operation has to be performed in the field, i.e., removing and discarding unpenetrable splice enclosure port plugs, or drilling a cable through bore in the seal assembly. Further, it has been found that when cables have been installed in the penetration ports or drilled bore holes so that the seal assembly can complete a cable splice housing, the seal is not entirely satisfactory. A room temperature vulcanizing (RTV) material, mastic, tape or sealant has to be employed in the field at the location of the cable and corresponding port or bore to provide the requisite sealing and protect the cable splice or through penetration sealing devices from environmental exposure, i.e. dust, dirt, vermin, chemicals, moisture, fire and toxic byproducts of combustion.
Further, it has been found that some seal assemblies are pre-manufactured to custom fit a particular size cable. The difficulty experienced with this type seal arrangement is that a relatively large inventory of seal assemblies is required for use with different size cables. What is desired is a single seal assembly which can accommodate different size cables.
Additionally, it has been found that, in some instances, when a particular seal assembly is installed at a job site, the components of the seal assembly, when crafted or tightened during installation, do not always provide for uniform sealing throughout the seal assembly. Rather, upon installation, the seal components generate uneven forces that sometimes produce an undesired seal assembly.
What is desired is a seal assembly which can be utilized with a housing, conduit, or cable splice assembly in which the seal assembly accommodates various size cables free of having to initially discard unpenetrable plugs and secondarily use excess inventory of craft sensitive materials, or perform a drilling operation in the seal assembly, either at the factory or in the field.
Further, it is desired to have a seal assembly which, when installed, provides the desired sealing characteristics in that the penetrating conduits or cables stored, spliced or protected by means of a cable housing or through penetration sealing device, are protected from adverse environmental exposures, i.e., dust, vermin, dirt, chemicals, moisture, fire and toxic byproducts of combustion.
Moreover, it is desired to have a seal assembly that is relatively installer friendly in that the seal assembly will permit various sized penetrating conduits or cables to be relatively readily utilized with the sealing assembly. Further, it is desired that the seal assembly be relatively easily assembled as a barrier seal and disassembled easily to accommodate cable penetration. Moreover, the seal assembly must be relatively easy to assemble or disassemble during cable installation, closure maintenance or repair and network expansion procedures.
The present invention relates to an improvement over the disclosure of co-owned Mitchell, U.S. Pat. No. 5,048,382, the disclosure of which is hereby incorporated by reference. This patent teaches methods for providing elastomeric sealing sleeves in which concentric rings are cut cleanly into the sleeve for substantially the entire thickness of the sleeve. Each ring is cut entirely about its circumference without unwanted serrations occurring in the sleeve. Briefly, in the process of the present invention, a molded, extruded or die-cut elastomeric sleeve having an appropriate size and shape is positioned on a chuck means whereby one side or face of the sleeve is maintained by a vacuum means against the outer face of the chuck.
A cutting machine, which holds a cutting knife, is indexed to align the knife relative to a selected position on the remaining side of the sleeve. The chuck and sleeve then are rotated at a desired speed whereby the sleeve is spun about a longitudinal axis. The cutting machine is actuated whereby the knife enters one side of the rotating sleeve and commences to cut a concentric slit into the sleeve.
As the knife progressively cuts into the sleeve, elastomeric sleeve material located contiguous to the outboard side of the knife separates slightly from the sleeve material located adjacent the inboard side of the cutting knife. Without being bound by a particular theory, it is believed that the separation of sleeve material in the vicinity of the knife blade is caused by the centrifugal force acting on the rotating sleeve. In other words, a small pocket is formed in the sleeve at least at the location of the cutting knife, the effect of which is to allow the knife blade to penetrate relatively cleanly and easily into the elastomeric sleeve such that a concentric ring is cut cleanly into the sleeve.
The cutting machine then is actuated whereby the cutting knife is retracted from the sleeve and indexed radially outward to a second location where a second concentric slit is cut into the face of the rotating sleeve. The process is repeated until the desired numbers of concentric slits are cut into the sleeve.
While cutting operations are performed on the sleeve, the sleeve and cutting tool are flushed extensively with a cooling lubricant to preclude excessive heat build up occurring in the sleeve and knife, the attendant disadvantage being that heat generated in the cutting operation tends to reseal adjacent sections of the sleeve which have been cut.
It is believed that the rotating sleeve generates a centrifugal force which serves to separate adjacent portions of the sleeve at least in the area where the knife is cutting the elastomeric sleeve. This material separation allows the knife blade to make a clean ring cut into the elastomeric material obviating serrated ring problems which existed in prior art practices, predating the Mitchell '382 patent. No talc-like material is required such that, upon completion of a cutting operation, an improved elastomeric sealing sleeve is provided having the desired number of concentric rings disposed therein. Moreover, one side or face of the sleeve is free of any cuts or nicks.
Despite the success of the method of the Mitchell patent for producing sealing devices there remain certain limitations in the Mitchell method as the needs of the telecommunications, utilities, construction and fabrication industries have matured. Specifically, the Mitchell method is particularly useful when the sealing devices having concentric rings are greater than 3 inches in diameter. As a function of their design, these large elastomers have a correspondingly large surface area which is beneficial when a vacuum is used to hold the elastomer against a rotating chuck. In this method, the proportionate surface area of the large elastomer created a requisite cavity to work with the vacuum, and the device could be successfully held against a rotating chuck in order that the procedures of U.S. Pat. No. 5,048,382 could be utilized.
One shortcoming of the basic method of the Mitchell patent is that the concentric rings are relatively thick, and while the end sealing washers were successfully utilized to limit exposure to weather in the original splice case products of GATM, U.S. Pat. No. 4,694,118, the thickness of this ring processing did not offer a pressure-tight, or hermetic seal around a penetrating cable. In this sense, the GATM splice case and its end seals are classified as free-breathing.
More recently there exists demand for a re-penetrable, elastomeric sealing device for the smaller cable ports of pressurized, and water proof electrical and telecommunication splicing enclosures. Due to the high bandwidth requirements of advanced copper connectivity solutions, cable broadband, fiber optic, and electrical transmission and distribution sealing enclosures, an effective and reliable pressurized enclosure(s) and/or sealing assemblies are necessary in order to protect the spliced/fused junctions of the conductors. Similar needs also exist with respect to duct-work, cabinets, structural bulkheads, through penetration sealing devices and the like.
Existing pressure-tight/watertight sealing enclosures have considerable mechanical strength properties within their design that they can provide a hermetic seal against the environment. However, an inherent weakness of these type of enclosures becomes apparent when it comes time to effectively seal one, and sometimes multiple penetrating conduit(s) or cable(s) of unknown manufacture and supply, thereby having an unknown outer jacket circumference. Moreover, it will sometimes be desired that several different outer jacket circumferences will penetrate an individual, multiple port enclosure or sealing device.
There exist several labor intensive, and craft sensitive means to seal single or multiple axes into a penetration port. However, these are secondary penetration methods which typically do not coincide with a means to initially seal off any unused penetration ports and provide for future expansion without wasteful disposal of inadequate port plugs. Several of the methods used to effectuate a penetration seal also require a considerable amount of time and material to wrap a continuous ply around a single or multiple penetrating axis. These methods enlarge the cable's nominal outer jacket diameter to an increased profile which will effectively engage within the inner molded profile of the corresponding cable port. These methods further require the inherent mechanical properties of the splice case, or sealing product to create an effective, pressure tight/water tight seal.
Sometimes known as “mastic-wrap” the continuous ply technique does not readily provide for an effective means to seal the interstice space between multiple cables. Multiple cable penetrations through a singular port is a desirable means to maximize the utility of existing splice protection enclosures and new deployment of various manufacturer's equipment in order to increase their serviceable deployment and provide maximum transmitting potential through a vast network of existing and expanded capitalized infrastructure.
There remains a desire in the art to provide original barrier seals which are designed to mechanically interface within the cable access/penetration port(s) profile(s) of various sized splice enclosures and through penetration devices. In the installed scenario, there remains a desire for pre-molded seals or grommets to achieve the same final product stage as the above referenced Mastic-Wrap in regards to its mechanical interface and seal engagement with the seal assembly. It is desired for such seal assemblies to first be an effective and un-penetrated barrier; for the seals to be capable of being field modified with little or no tools so as to minimize expensive craft sensitive labor. It is further desired to eliminate waste created by removing and discarding the heretofore undesirable and un-penetrable port plugs. Further, it is desired that the seals be pre-engineered to accommodate single, as well as multiple axes of penetration. It is thereby desired to provide improved methods for producing smaller sizes of seals having single as well as multiple axes of penetration. In particular, improved methods for producing seals having concentric sizing rings which seals are less than 3 inches in diameter are desired.
It is also the case that with smaller diameter cables, such as fiber optic cables that finer gradations of ring thicknesses are needed than is the case with larger diameter copper cables. This is because the smaller circumferential surfaces of such smaller cables have reduced sealing surfaces and thus require a closer “fit” between the sealing rings and the cable. The method for cutting the sealing blanks therefore must be more precise in order to meet the closer tolerances demanded by the use of smaller diameter cables.
While vacuum fixturing and the rotation of small elastomeric shapes is possible, any attempt to cut into the rotating device to process a plurality of rings according to the methods of the '382 patent will cause it to disengage from the revolving fixture. Disengagement from the rotating chuck therefore not only makes ring-cut processing impossible, but also is a serious safety hazard for either a machine operator or an equipment hazard in that the manufacturing process equipment will have uncontrolled exposure to loose, flying parts. Accordingly, there remains a need in the art for improved methods for producing small seals having one or more series of removable concentric sizing rings.